A fluorene derivative such as 9,9-bis(4-(2-hydroxyethoxy)phenyl)fluorene shows promise as a material for production of a polymer having a high heat resistance, a high transparency, and a high index of refraction (such as epoxy resin, polyester, polyether, and polycarbonate). In recent years, the fluorene derivative has been expected to be used as a raw material of an optical lens, a film, a plastic optical fiber, an optical disc substrate, a heat-resistant resin, and an engineering plastic etc.
In order to produce stably polymers which are excellent thermally and optically in these applications, the following conditions are important, for example: (i) a molecular weight and molecular weight distribution are controllable, and (ii) a content ratio of un-reacted monomers and/or a content ratio of un-reacted oligomers is low. Further, it is desirable that 9,9-bis(4-(2-hydroxyethoxy)phenyl)fluorene monomer, serving as a raw material, (i) maintains constant physical properties, (ii) has high purity, and (iii) has high reactivity. Meanwhile, a certain sort of a solid has a polymorph which is represented by a certain chemical formula but has a plurality of different crystal structures. A pseudo-polymorph and a non-crystalline form are regarded as a sort of polymorph. Such polymorphs are different from each other in physical properties (such as density, a melting point, and solubility), and have a significant influence on physical properties of resultant polymers, and/or reactivity, which polymers are obtained with the use of the polymorphs. Accordingly, controlling a crystalline form of a raw material is one of important factors in realizing a more excellent polymer. For this reason, a lot of effort has been made to (i) find a specific crystalline form or a specific non-crystalline form and (ii) prepare such a specific form.
Further, a non-crystalline solid has transparency, homogeneity, isotropy, and excellent workability. Such a non-crystalline solid shows promise as a photonics material such as an organic electroluminescence element, a recording element, a storage element, an electrical field sensor, and an optical sampling oscilloscope. Particularly, a non-crystalline low-molecular-weight organic compound has attracted attention in recent years as a resist material having high resolution and low roughness. However, unlike a high-molecular-weight compound, a low-molecular-weight organic compound is in general highly likely to be crystallized and unlikely to have a non-crystalline form. Such a low-molecular-weight organic compound is generally in a form of crystals at a temperature equal to or lower than its melting point. The non-crystalline form may be seen, for example, in a medical product that has a complex structure. However, the non-crystalline form is thermodynamically in a nonequilibrium state and is unstable as compared with a crystalline form. Accordingly, the non-crystalline form is easily subjected to transition, so that recrystallization occurs. Therefore, finding a non-crystalline low-molecular-weight organic compound which can easily form a stable glass state is significantly important, even in terms of creating a new functional material which is different from a conventional non-crystalline polymer or a conventional polymer composite material.
Examples of a method of producing 9,9-bis(4-(2-hydroxyethoxy)phenyl)fluorene encompass a method of causing fluorenone and phenoxyethanol to be subjected to dehydration condensation, by use of sulfuric acid and thiols as catalysts (Patent Literature 1), and a method of causing 9,9-bis(4-hydroxyphenyl)fluorene and ethylene carbonate to react with each other (Non-Patent Literature 1). Further, we made a patent application of a novel production method (Patent Literature 2), which is different from the methods described above.
Moreover, as a crystalline form of 9,9-bis(4-(2-hydroxyethoxy)phenyl)fluorene, Patent Literature 3 discloses that there is a polymorph (hereinafter, referred to as “polymorph B”) having a melting point in a range of 150° C. to 180° C., other than a polymorph (hereinafter, referred to as “polymorph A”) having a melting point in a range of 100° C. to 130° C., which polymorph A has been conventionally known. However, it has not been known that there is another crystalline form or a non-crystalline form of 9,9-bis(4-(2-hydroxyethoxy)phenyl)fluorene, other than the above two sorts of polymorph.
Citation List
[Patent Literature]
[Patent Literature 1]
Japanese Patent Application Publication, Tokukaihei, No. 7-165657 A (1995) (Publication Date: Jun. 27, 1995)
[Patent Literature 2]
Japanese Patent Application Publication, Tokukai, No. 2007-23016 A (Publication Date: Feb. 1, 2007)
[Patent Literature 3]
Japanese Patent No. 4140975 B (Publication Date: Jun. 20, 2008)
[Non-Patent Literature]
[Non-Patent Literature 1]
Journal of Applied Polymer Science, 1995, Vol. 58, 1189-1197